In general, for example, in the case that one person (listener) listens to the speech of the other person (speaker), when the listening capability, e.g., a speech recognition critical speed (maximum speech speed at which the speech can be precisely identified) of the listener is declined because of aging or any disorder, it becomes often hard for the listener to identify the speech with an ordinary speed or the speech of rapid talking. In such case, normally the listener can make up for the listening capability by using a so-called hearing aid.
However, the conventional hearing aid which is used by the person having declined listening capability or hearing disorder can simply make up for propagation characteristics of an external ear and a middle ear in an auditory organ by virtue of an improvement of a frequency characteristic, a gain control, etc. Therefore, there has been such a problem that decline of the speech identification capability which is mainly associated with degradation of an auditory center cannot be compensated.
In light of the above, recently a speech speed controlled type hearing aiding device has been thought out which can aid the hearing by processing the speech of the speaker such that the speech speed can be adjusted for the listening capability of the listener in substantially real time.
According to this speech speed controlled type hearing aiding device, by executing an expansion process for expanding the speech of the speaker in time, and then storing sequentially the speech obtained by the expansion process into an output buffer memory, and then outputting stored speech, the speech speed of the speaker is changed (slowed down) to compensate the decline of the listening capability of the listener.
However, in the above speech speed controlled type hearing aid in the prior art, there have been problems described in the following.
To begin with, the speech speed controlled type hearing aid in the prior art expands the speech data input as described above by the expansion process, then stores sequentially the speech data obtained by the expansion process into the output buffer memory, and then outputs the stored speech data. Therefore, for example, in case the listener wishes to slow down the speech speed much more or restore the speech speed into the original speed in the middle of listening, the speech speed cannot be restored into the original speed until all the speech data which are stored in the output buffer memory have been output.
For this reason, there has been a problem that, in order to restore the speech speed in the middle of listening, a considerably long delay in time is caused until the existing speech speed can be restored into the original speed.
In addition, such speech speed controlled type hearing aid in the prior art can be employed by not only the above listener who has the declined listening capability but also the listener who has the normal listening capability but wish to listen to the foreign language, for example, in the application field to change (slow down) the speech speed of the speaker in order to compensate their listening capability. However, in this case, there has been a problem that, like the above, a time delay is caused upon changing the speech speed in the middle of listening.
The present invention has been made in light of the above circumstances, and it is an object of the present invention to provide a speech speed converting method and a device for embodying the same which is able to convert the speech speed of the output voice to follow instantly an operation of the listener, and thus to improve extremely the convenience of use on the listener side.